Use of high energy ball milling and porosity control in the development of Ti-Nb-Zr alloys for biomedical applications.

• Grant number: 10/09219-7
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: September 01, 2010
• End date: February 28, 2013
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Durval Rodrigues Junior
• Grantee: José Luiz Minatti
• Host Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil

Abstract

Among the metallic biomaterials, titanium alloys have been highlighted in relation to more conventional materials, like stainless steel and cobalt alloys. In recent years, alloys of the Ti-Nb-Zr system were developed showing high mechanical strength and corrosion resistance, and low elastic modulus due to the b-Ti stabilizing phase (Nb, Zr, etc.), which also are non-cytotoxic elements. However, even these alloys have elastic modulus greater than the bones and, therefore, materials with controlled porosity are preferable, even because they allow better osseointegration. In this work it will be evaluated a new processing route of Ti-Nb-Zr porous alloys, via powder metallurgy, which do not require additional surface treatments (coating and/or chemical treatment). However, the powder metallurgy brings the possibility of segregation during the processing steps and limits the sizes and shapes of the produced parts. To address these problems, it will be used high-energy ball milling to reduce and standardize the grain sizes of the alloys, in addition to achieving the desired stoichiometry as a function of the phase transformations during milling. The powders will be mixed with a space-holder agent and then submitted to the conformation by starch consolidation, technique poorly explored to obtain metallic alloys that allow greater versatility of shapes and sizes, with controlled porosity. The specimens will be subjected to calcination (debinding) to remove the space-holder agent, and then heat treated under vacuum. The control of porosity and final density will be achieved varying the powder particle sizes, the content of the space-holder agent, and the heat treatment profiles. The characterization tests will be microstructural, superficial and mechanical.